Final Flashcards
The shape of teeth tells us…
something about the animals ate and how they process their food-can help you infer what they ate, their diet-digestion, breaking down nutrients
2 parts of digestion
-physical digestion (mostly teeth-but for some dinos not at much) and chemical digestion (in the stomach)
Dinosaurs (and other groups) have a ___ dentition
thecodont dentition
thecodont dentition
teeth set in sockets -means that their tooth has a root that’s in a socket in the jawbone-like our teeth-all archosaurs have that
most vertebrates are ____ (in relation to dentition)
homodont
homodont
- means teeth same shape throughout jaw
- almost all animals have this characteristic
- so are (most) dinos
most mammals are _____ (in relation to dentition)
heterodont
heterodont
- different shaped teeth throughout your mouth
- canines-front teeth to cut, molars and premolars-can be blades or flat
heterodontosaurus
- whole group of dinos that are heterodonts
- means the organisms can eat a variety of diff food-diff tooth shapes allow them to process diff kinds of food
2 types of tooth replacement:
Polyphyodont, Diphyodont
Polyphyodont
(generations of teeth-fish-amphibians, reptiles)
-tooth replacement continues throughout life (replace teeth throughout life-constantly losing teeth and getting new ones)
Diphyodont
(mammals)
-only 2 generations of teeth-like humans-baby teeth then adult teeth, if get adult teeth removed then no new teeth will grow in
dinos were ____
polyphyodonts
One the adaptations for better chewing in mammals (polyphyodonts or diphyodonts?):
being Diphyodonts-they have only two sets of teeth, juvenile and adult.
- usually have fewer baby teeth and more adult teeth
- all mammals do this-have 2 generations of teeth
- having these 2 generations of teeth means once adult teeth come in, the top and bottom teeth will always be the same teeth touching each other-means top and bottom teeth fit together like a little puzzle-precise occlusion
- This allows for precise occlusion
precise occlusion
-the bringing of opposing surfaces of the teeth of the two jaws into contact, i.e. when lower teeth meet upper teeth as the mouth is closed
Diphyodonty and heterodonty allowed for…
…chewing in mammals. This was a key adaptation for processing plant matter
chewing is pretty ___ in the tetrapod world
- unique
- most animals don’t chew-most animals take big hunk of meat off and swallow it
- mammals chew-most animals don’t
- allows for processing plant matter
Plant matter is ___
- tough
- The cuticle on leaves is hard to break down
- Also, grasses may have lots of grit
- AND leaves are nutritionally poor, so you have to eat a lot of them…
how do mammals solve this (plants being tough to digest/nutritionally poor)?
-Mammals solve this with hypsodonty (tall teeth) -need to grind up plant material a lot-covered in dirt-will wear down teeth a lot-so long teeth so have time that even if wear down will still have teeth-also grinding will give them ridges, helpful in more grinding
so, herbivore teeth tended to be ____
- tall, and relatively flat with lots of ridges
- lots of ridges-scrape against each other, that’s how they grind up plants
- elephants do this, so do rats
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Sauropods:
have gastroliths -basically they swallow rocks, have area in gut that’s muscular-plant material came into stomach with rocks, squeeze it all together to break down plant material using the rocks and grit
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Thyreophorans and ceratopsians
gut fermentation -swallowed plants whole and let them rot in their guts-once they start to rot, releases some of the nutrients and able to get nutrients after plant has broken down over natural process of plants breaking down over time-some primates did this too
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Hadrosaurs and Ceratopsians:
dental batteries
Dental Batteries
- some groups found a way around this Polyphyodont thing to find a way to chew-not like mammals do but found a unique way to chew-developed these things called dental batteries-basically a line of teeth-growing from the bottom up-older teeth at the top-at the top do the grinding-conveyor belt of teeth (works cuz constantly growing new teeth)-teeth constantly growing, grinding them down at the top
- Hadrosaurs and Ceratopsians
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? hadrosaurs:
cranial kinesis
cranial kinesis in hadrosaurs
-hadrosaurs developed whole new way to chew-mammals can chow cuz can move jaws from side to side-dinos couldn’t do this motion allowed by your lower jaw-took advantage of their cranial kinesis-our only joint is at jaw-dinos have kinetic skulls so all kinds of joints up in head-as the lower teeth come up, hit upper teeth and push them out, then there’s a little point so cheeks at the top flap out-that motions causes grinding-so when chew, not side to side, but cheeks going in and out as chew
ornithiscians had a ____
predentary bone
predentary bone in ornithiscians
-basically had little beak for helping tear off things and bring into mouth-nip off plant material and pull into mouth-nail like keratin material in front of mouth instead of teeth-modern horned mammal has this and looks like some dinos had it too
Dinosaur cheeks
- need cheeks to chew-food will spill out of mouth without cheeks
- so dinos that chew probably had cheeks, while carnivore dinos probably didn’t-no cheeks-cuz no processing in mouth-doesn’t need cheeks-just swallow whole
Eating meat is ____ (easy/hard)
- easy
- Just tear off a chunk and swallow
- Meat is relatively easy to digest-got lots of enzymes that can break down meat easily
- Requires blade-like teeth for tearing & cutting flesh
- Also, simple conical teeth for puncturing/ killing
T rex had ____ teeth (big/small)
T rex had giant teeth-probably for just killing, didn’t do much chewing-probably didn’t even do much tearing with teeth-just yanking into mouth then swallow whole
cats cup up food with ____
- side of jaw
- raspy tongue cleans meat from bone
- kill with front teeth, blade like teeth in back fro cutting up chunks to eat
mammals tend to have more ___ teeth for ____
- slicing, cutting
- cuz don’t swallow things whole-not doing much chewing though if carnivore
Tooth Serrations
Tooth Serrations
- Serrations help hold what is being cut in place
- Also help with keeping the edge sharp
- Can also hold bacteria only some groups-some debate about it (e.g., Komodo dragon)
- theropod teeth serrated
skull and lower jaw also hold clues to feeding in mammals-hyena vs rabbit jaw
- hyena jaw more scissor like, good for tearing-like sideways V
- rabbit jaw-2 Ls on their backs, connect at bottom of L-having jaw above the tooth bone-allowed teeth to meet at same time-good for grinding
masseters
- in herbivores, like warthogs
- allow to do side to side motion-emphasize those muscles so can do side to side grinding
a warthog is a plant eater-so why are there giant teeth at the front?
- this is where things get complicated-sometimes see herbivores with big pointy teeth
- usually when see in herbivores-some kind of sexual selection-male warthog, uses big teeth to show how sexy is, attract mates
Dino jaw shape
- same thing as before, first type of jaw (seen in T rex) is good for meat eating (like V)
- second one (2 Ls-but now like lying on so small part of L faces down on left side-so joint below bend)-herbivores-instead of jaw bone being above tooth growth, it’s below-but effect is the same-teeth will meet at the same time to do grinding
Specialized Teeth - Piscivores
- Fish-eaters tend to have long, thin snouts with homodont, pointed teeth for catching fast fish-fish are really fast so need jaw that will close really fast and has little tiny teeth to grab onto them
- long snout
- some dinos were probably piscivores as well-ate fish
Spinosaurs and Pterosaurs
- think ate fish cuz adaptations/characteristics similar to others that did
- pterosaurs-not dinos but closely related
- some specialized dinos needed specialized teeth-other types of specialized teeth or having no teeth-these are just examples of how teeth can show diet and how ate
Dinosaur Physiology
- meaning how got energy, what did they use it for
- Cold-blooded vs. Warm-blooded Dinosaurs-this is argued-most say somewhat warm-blooded, but neither of these terms are very good-better terms to describe it, also this is too dichotic-2 poles-many animals, like dinos, are more in the middle
Types of Metabolism
- Endotherms – generate heat internally
- Ectotherms – need external sources of heat
- Homeotherms – maintain constant internal body temperature
- Poikilotherms – body temperature varies, usually in relation to the environment-goes up and down depending on what’s going on in environment
- (most) Mammals and Birds – endothermic homeotherms-generate heat internally, use to keep relatively constant body temperature
- (most) modern “reptiles” – ectothermic poikilotherms
Endotherms
generate heat internally
Ectotherms
need external sources of heat
Homeotherms
maintain constant internal body temperature
Poikilotherms
body temperature varies, usually in relation to the environment-goes up and down depending on what’s going on in environment
endothermic homeotherms
- (most) Mammals and Birds-but also some fish and insects (exception)-and bats + some bird endothermic poikilotherms (exception)
- generate heat internally, use to keep relatively constant body temperature
ectothermic poikilotherms
- (most) modern “reptiles”-except some large reptiles (exception), which are ectothermic homeotherms
- most fish, amphibians, reptiles, and most invertebrates-body changes due to environment, external sources of heat from environment
Exceptions prove the rule…
- Bats and some birds endothermic poikilotherms (also hibernating mammals)
- Some fish and insects endothermic homeotherms
- Some large reptiles ectothermic homeotherms
which is better? endothermy or ectothermy? or poikilotherms? or homeotherms?
No way is better than another-all about tradeoffs, each has own benefits and costs
Endothermy benefits
– Sustained activity
– Active at night
– Adaptation to cold environments
Endothermy costs
– Requires LOTS of food - 10-30x similarly sized ectotherms
– Not efficient at small body sizes…why? (has to do with surface area/volume ratio)
Ectothermy benefits?
– Adaptation to hot environments
– Need little food
Ectothermy costs
(primitive condition-but that’s okay)
– Capable of only short bursts of activity
– Limited ability to be active at night
why is endothermy not efficient for small body sizes? SA/
-Surface Area/Volume relationship
Surface area/volume relationship
- if small, most of matter is closer to the surface-less volume relative to surface area-high surface area to volume ratio
- if bigger, stuff in middle that’s farther from the edges/outside-a lot more volume relative to the surface area-low surface area to volume ratio
- so larger animals tend to have a lower SA:V ratio/low SA compared to volume compared to that of smaller animals
why is this SA:V ratio important?
-The surface area of an animal is where it exchanges heat with the environment-small endotherms have a problem retaining heat cuz high SA to V ratio-big endotherms have problems dumping heat-may overheat-so big animals like elephants tend to have big radiators-like big ears on elephants-to increase SA
Small endotherms have a problem with ____
retaining heat (because they have high SA/V)
Large endotherms have a problem with ____
dumping excess heat (because they have low SA/V)
SO, mammals (endotherms) tend to be (in regards to size) ____
no smaller than a few inches
ectotherm size (can they be smaller than a few inches?)
-doesn’t matter if ectotherm-actually better to smaller-can get really tiny
Gigantothermy
- Large animals retain heat
- So large ectotherms can be homeothermic…
So what about dinos?
- If they were endotherms did they overheat?
- If they were ectotherms were they gigantotherms?
- what were dinosaurs?! Ectotherms? Gigantotherms? Endotherms?
- Were they all the same?!
- this is why there’s such big debate about dinosaur endo vs. ectothermy
- cladogram doesn’t really help here-ectotherms primitive trait-endothermy evolved somewhere-but we don’t know where-the 2 living groups that are on either side of the dinos-birds and crocs-are different-so that doesn’t really help us. Could mean endothermy evolved on before or after dinos
What lines of evidence can we use to solve this…? (if dinos were ectothermic/endothermic/etc.)
- Cardiopulmonary evidence – hearts & lungs
- Insulation
- Bone and growth rates
- Neurophysiology – relative brain size
- Isotopic evidence
- Skull features – turbinates
- Posture – bipedality & running
- Biogeographic Distribution – Do we find dinosaurs in cold places?
Cardiopulmonary evidence-hearts
-what’s interesting is that hole area-people think there may have been a heart there-think can even see chambers within the heart-know all modern endotherms have a 4 chambered heart-4 chambered heart tends to be much more efficient in terms of pumping oxygenated blood around-mammals and birds have a 4 chambered heart-but it turns out that doesn’t help us very much, cuz it turns out crocs also had a 4 chambered heart-so the fact that they found a 4 chambered heart in that dino isn’t that surprising-this bracket below tells us that dinos probably had a 4 chambered heart -now there’s some question about whether it’s the same 4 chambered heart in crocs and birds, whether it’s homologous, or if it’s an analagous thing-did they evolve them convergently or separately-some debate about this-turns out 4 chambered hearts in crocs are a little different and mostly used less because of their efficiency in pumping, more cuz of thier efficiency for diving, so crocs have a special shunt that they use in their blood supply and circulatory system when they’re diving to preserve oxygen and things like that-the point here is that the fact that finding the 4 chambered heart in this dino isn’t particularly surprising-it may hint that they are endotherms, but the fact that crocs have them tell us that this isn’t particularly conclusive
Cardiopulmonary evidence-lungs
Bird Lungs:
- Bird have a number of air sacs connecting to their respiratory pathway -basically just dead spaces of air-there isn’t oxygen exchange happening in them-that only happens in the lungs-but basically these air sacs that are connected to the respiratory sac that extend into parts of their skeleton and parts of their axial skeleton and things like that that kind of fill up their body-fill up their spaces with these air sacs
- This (these air sacs) allows for more efficient one-way airflow during breathing
- what happens is they breathe in, air goes into air sacs, no oxygen exchange happens, and then on the next breath that air moves across the lungs, and then on the next breath it gets moved out-takes them 2 full cycles of respiration to get air in and out-this allows for very efficient oxygen exchange when air goes across the lungs-in mammals, breathe air in, goes into lungs, sits there for a while doing nothing-in this case, the air is always moving through the lungs, and that actually allowed for more efficient oxygen exchange (called countercurrent flow)-birds need this-flying is costly in terms of oxygen-need oxygen to fuel muscles used for flying
- mammals and birds (endotherms) have high oxygen demands, birds even more so than mammals
- if were to see these kinds of air sacs in dinos, would imply there’s some sort of high oxygen demand
- It seems that some dinosaurs had air sacs too, similar to modern birds
- air sacs in sauropod vertebra-probably filled with air-a number of air sacs wrapped around vertebrae
- the fact that dinos had air sacs speaks to the fact that maybe they were endotherms, like birds and mammals are
endotherms tend to breathe ___ than ectotherms
- more
- have higher respiration rates-ectotherms like snakes don’t breathe as often-cuz metabolism relatively low-main reason breathe in oxygen is to help you break down food taking it-so cuz don’t eat that much food don’t need as much oxygen-mammals and birds on the other hand have high oxygen demands, birds even more so than mammals
and it seems crocodiles had ____ (in relation to breathing/lungs)
- have 1 way breathing too
- but don’t do it the same as birds-like the way their 4 chambered hearts aren’t the same as birds-do it slightly differently, has more to do with diving in crocodiles-so that tells us that maybe the air sacs in dinos weren’t for efficient breathing-this study is only a couple of years old-the fact that we’re just finding this out about crocs points out that there’s a lot of stuff out there about animals that we still don’t know-lots of work to still be done even about living animals
Insulation evidence
- Only modern endotherms have insulation (something to insulate their bodies)
- Birds have feathers
- Mammals have fur
- It seems that many dinosaurs had feathers too… maybe not as many as modern birds but just the fact that dinos had any insulation at all points to dinos being endotherms-cuz helps you keep in the heat that you’re generating
- we find more and more evidence for feathered dinos every year
Bone Growth evidence-human bones
- our bones are not solid-are hollow on the inside-solid part on the outside called compact bone-and then on the inside the bone is either hollow or has spongy looking bone-it’s within this space (in hollow part or holes in sponge) where you have marrow
- we’re gonna be looking more at the compact bone-the diff between endotherms and ectotherms of their compact outside area of bone
- most of bones in body start off with cartilage model-later gets replaced by bone, first shaft then ends-then growth plate between the shaft and ends of the bone-that’s how bones grow
- the growth plate is key-limits how big you can grow-so we have a determinate growth
- reptiles on the other hand have what’s called indeterminate growth
Bone Growth evidence-endotherms vs. ectotherms
-endotherms tend to have determinate growth and ectotherms tend to have indeterminate growth
determinate growth
-predetermined how tall we can be when born-nutrition can affect this but for the most part mammals and birds have determinate growth
indeterminate growth
growth happens in similar way, but no growth plan-body just keeps adding more and more bone on the outside of a bone, bone keeps getting bigger and bigger-reptile can grow indefinitely-growth rate slows down over time, but never stops
Bone Growth evidence-bone microstructure/compact bone (in mammals)
- the other thing we want to look at inside the bone is look at that compact bone in more detail
- compact bone actually isn’t solid, is only mostly solid-has some blood vessels running through it-because bone is a living material-it grows, it has cells that are constantly remodeling, it turns out 5-10 years from now all of your bone will be diff from the bone you have now, because slowly replaced with new bone-so it’s highly revascular, has lots of blood vessels-and it’s always being remodeled, reworked-reworking is often unorganized-if you look at it up close, see bulls-eye like structure, called osteon-in the middle of it is a blood vessel/where the blood vessels go called the haversian canal-and all the dark parts are where a bone cell lives (what’s called a osteocyte)-they’re constantly reworking bones-break down osteons, rebuild new osteons-constantly rebuilding that bulls-eye structure-and they don’t do it with a whole lot of organization-sometimes mammalian bone is called “woven” because it’s disorganized like this-with lots of layers all over each other and reworked
Bone Growth evidence-bird bone
- similar to mammalian bone
- same reworked, woven bone-not organized, random placement of osteocytes-tends to be relatively random
Bone Growth evidence-Lines of arrested growth (LAGs)
- another thing we see in bones, especially those of ecotherms
- definition: Characterize times of slowed/stopped growth
- ectotherms are constantly laying down bone on the outside so they can grow indeterminately-that growth doesn’t happen continuously-grows for a little, then stops for a while, then grows again, then sits for a while, etc.
- can see this stopping and starting in what are called lines of arrested growth
- tend to be on annual cycles-when it gets cold ectotherms, generate their heat internally, so they tend to stop growing because they can’t put their resources/energy into growing because they’re putting energy into staying warm-so they don’t grow in the winter months-then they grow when it gets warm out
- because lines of arrested growth have to do with changes in temperature, tend to be seen more in ectotherm
- Similar to tree rings-grow in spurts then stop-looking at them gives hint to past/climate of past
Bone Growth evidence-Dinosaur bones
- dinosaur bones, when you look at them in crossection, are often woven like bird and mammal bones, with disorganized growth-but, they also sometimes have LAGs, which speaks to some sort of arrested growth that’s going on-a little equivocal-bones that sometimes look like mammal and bird bones, but also sometimes like reptiles
- but there’s another twist to this story: it turns out that sometimes mammals get LAGs too-certain mammals, esp those who live in environments that are highly variable, often get these LAGs-usually looks random and woven but every once in a while get some LAGs-this is similar to dinos-so maybe the fact that dinos have these LAGs is not that big of deal, doesn’t say much about endothermy vs. ectothermy-so this bone growth stuff is a little unclear
BUT, it turns out…(in relation to LAGs/exception to rule)
some mammals get LAGs too
Growth Rate evidence-mammals and birds
- tend to have a 3 part growth curve:
- Slow growth as infants and toddlers
- Fast growth as juveniles and adolescents
- Slow growth (or stopping) as adults
Growth Rate evidence-ectotherms
-tend to have a relatively constant growth rate-does slow down as gets older but don’t have this 3 part growth curve
Growth Rate evidence-Dinosaur growth rates
- Dinos had a 3 part growth curve, especially the biggest ones
- They also grew at rates faster than birds or mammals-the large ones are putting on 10s of kg a day (during their time of highest growth rate)-literally 20 lbs a day-pretty extreme-the fact that they’re extreme is more similar to endotherms than ectotherms-some mammals do this, like whales
- Large sauropods: 20 kg/day (similar to whales)
- Large theropods: 2 kg/day (similar to birds & mammals)
- Small-mid-sized: 1-800 g/day
Growth Rate evidence-Dinosaur life spans
- Large sauropods: 50 yrs
- Large theropods: 30 yrs
- Small to mid-sized: 7-15 yrs
- Smallest: 3-4 yrs
Growth Rate evidence-Dinoaur growth rates and life spans in relation to ectotherms/endotherms
-All of this is similar to modern endotherms-pretty similar to modern mammals if scale them up to these sizes-the fact that dinosaur growth compared to life spans are similar speaks to this
Growth Rate evidence-Encephalization Quotient
- Ratio of brain size to body size
- brains are metabolically expensive, meaning that it takes a lot of energy and oxygen to keep brains going-so only animals with access to a lot of energy and oxygen have large brains
- one way we measure the size of brains is not absolute size, cuz then would say whale have bigger brains than humans-what we use is relative brain size-ratio of brain size to body size-called the encephalization quotient
endotherms have a ____ Encephalization Quotient
- high-because brains are expensive
- humans have a very big brain for their body size
Growth Rate evidence-Encephalization Quotient
- Dinosaurs show a range of encephalization quotient, with some similar to modern birds
- some really small brains-but some ornithopods and some meat-eating dinos have pretty big brains, similar to birds
Isotopes and Body Temperature evidence
- Different isotopes have different weights (Why?) has to do with the fact that they basically have diff number of neutrons-C 12 and C 14 act the same chemically cuz have the same number of protons-but have diff numbers of neutrons so C14 is heavier-neutrons don’t have anything to do with chemicals to C14 acts just like C12-could make CO2 out of C14, carbon in bodies out of it, and so on and so forth. It’s just a little heavier.
- Lighter isotopes are preferred in most chemical reactions though-it’s easier to move them around because they’re lighter-chemical reactions driven by heat, the heat tends to move things that are lighter rather than heavier-lighter tend to be more incorporated into chemical reactions
- At higher temperatures this difference between the 2 becomes less -at low temperatures the C12 is more preferred than the C14-but as get higher and higher temperature the difference between the 2 doesn’t matter as much -at higher temps, the diff of weight doesn’t matter as much, because there’s enough heat to move whatever you want around
- use this to tell relative body temps on species (temp at extremities vs. core)
Isotopes and Body Temperature evidence-what this means for ectothermy/endothermy
-Extremities on the body (e.g., limbs and tails) will be colder in ectotherms-lizards get very cold hands and feet-keep whatever heat they’ve got in their core-what this means is that there’s less of a diff in temperature between the core of an ectotherm, like you, and its fingertips-in an ectotherm, there’s a big diff in temp between these 2 places-this means basically the diff in isotope usage between the extremities won’t vary very much because the temperature’s pretty similar-but in ectotherms huge diff in isotope usage between core and extremities because extremities so much colder so harder to move heavier isotopes around
-large modern lizards (like kimodo dragon) tend to have bigger differences between tail/extremities and core than dinos-dino differences in temp between extremities and core more comparable to mammals
(this is all relative, not absolute temps)
Isotopes and Body Temperature evidence-large modern lizards
(like kimodo dragon) tend to have bigger differences between tail/extremities and core than dinos
Isotopes and Body Temperature evidence-dinos
dino differences in temp between extremities and core more comparable to mammals-not as large differences as lizards
Isotopes and Body Temperature evidence-Absolute Measures of Temperature
-Uses “clumping” of isotopes at different temperatures-when they do this and look at dinos to find abs temp-looks like dinos had relatively high body temps-similar to endotherms
Skull Features evidence
- Mammals and birds have unique structures in their nose, the turbinates that make their breathing more efficient -little bony structures in the nose, covered in epiphelium, covered in tissue, that makes a bunch of snot-it also has a lot of blood vessels in it
- what happens is, as the animal breathes in, cold air from outside goes across those turbinates that are covered in snot and picks up moisture and heat, and that in turn goes down to the lungs-lungs better at getting oxygen out of warm moist air-when mammals breathe, breathe a lot, high respiration rate,want to get as much oxygen as possible, so wanna do this is the most efficient way-this way gets more oxygen, is very efficient-helps maintain heat and moisture
- don’t want to lose all that moisture and heat, so what happens is when the air goes back out, that air dumps its heat and dump its moisture onto the turbinates, then just air is breathed out and it’s relatively cool-creature conserves that heat and moisture
- animals that run a lot (pursuit predators not pounce predators-chase their prey down) have more complex turbinates cuz need to be more efficient in breathing
Skull Features evidence-turbinates-what happens when breathe in
- what happens is, as the animal breathes in, cold air from outside goes across those turbinates that are covered in snot and picks up moisture and heat, and that in turn goes down to the lungs-lungs better at getting oxygen out of warm moist air-when mammals breathe, breathe a lot, high respiration rate,want to get as much oxygen as possible, so wanna do this is the most efficient way-this way gets more oxygen, is very efficient-helps maintain heat and moisture
- relatively cool, dry air passes over moist, warm turbinates and is heated and saturated with water
do humans have turbinates?
yes, except they’re pretty little one-3 on each side, look like little commas-not as cool and intricate as dino ones
Skull Features evidence-turbinates-what happens when breathe out
- don’t want to lose all that moisture and heat, so what happens is when the air goes back out, that air dumps its heat and dump its moisture onto the turbinates, then just air is breathed out and it’s relatively cool-creature conserves that heat and moisture
- warm, most air passes over cooler, drier turbinates and transfers heat and moisture to their surface
-animals that run a lot (pursuit predators not pounce predators-chase their prey down) have ____ turbinates
more complex turbinates, cuz need to be more efficient in breathing
Skull Features evidence-Function of Turbinates
1) Condition incoming air
2) Conserve heat
3) Conserve water
Because: High ventilation rates* in endotherms create a water and heat conservation problem
*Ventilation rate = breaths/minute
Skull Features evidence-Did dinosaurs have turbinates?
- Turbinates don’t fossilize well-tend to be broken in fossils-hard to find specimens that still have these specimens inside nose
- Use nasal volume (how big it is) as a proxy for how many turbines in it
- dinos fall on reptile line-so probably did not have turbinates, which is something we associate with endotherms-mammals have them, and birds do too, but cartilaginous (made of cartilage) in birds-ectotherms don’t have them-dinos don’t have them, except then new study
- study from about 5 years ago, actually think they did have turbinates-did same sort of CT scans across the nose-did some modeling-think dinos did have at least very simple sorts of turbinates-the evidence is a little unclear, just like everything else so far
Postural Evidence-lizards
- lizards are sprawled, arms out on sides-runs side to side
- lizards, when run, run side to side-air gets compressed, pushing air from 1 lung to another (expanding) moves from one side to the other-instead of air moving in and out of mouths, moving back and forth and side to side
- lizards, if chase them, eventually slow down, cuz used all their heat/energy-but also because can’t breathe well while running-can’t get oxygen in while they’re running
Postural Evidence-dinos
-have upright posture with their legs not on their sides but underneath them-legs run underneath body (like mammals)
Postural Evidence-mammals
- have upright posture with their legs not on their sides but underneath them-legs run underneath body-for 4 legged mammals
- upright posture allows mammals to time their breathing with their running
- mammals, with legs beneath them, can actually time breathing and moving legs/running together-mammal takes a big step forward, breathes in, then breathes out-can time this-expands chest, breathe in-compressed chest-then breathe out-can time those things together-remember mammals use a lot of oxygen-so if can use oxygen more efficiently, means can run longer distances, run more efficiently
- mammals can breathe while running-this has to do with this endothermy
Postural Evidence-crocodilians and mammal-like reptiles
-crocodilians and mammal-like reptiles somewhere in between, have semi-sprawling gait-you might expect that since midground between this and that-crocs a little weird, a little diff, peculiar
Postural Evidence-dinos, birds, and humans-why are they diff?
-dinos, birds, and humans are diff cuz they’re bipedal-moving just on hindlimbs-not doing this sort of thing
Postural Evidence-how this relates to dino endothermy/ectothermy?
- there still is a sort of timing of breathing to walking, even if only walking on 2 limbs-but a little diff
- the fact that dinos walk upright, have limbs beneath them, shows they’re more like endotherms than ectotherms
Biogeographic Evidence
- Dinosaurs did live near the poles-like Antarctica
- Modern ectotherms don’t-don’t tend to get ectotherms near the poles-can’t absorb enough heat
- BUT, the Mesozoic was a much warmer time
- so maybe the fact that they lived at poles doesn’t mean too much
- Maybe dinosaurs migrated-maybe what they did to avoid being too cold was just keep moving to the warmest places
- but still, the fact that we find dinos at the poles is pretty interesting-and looks like some dinos lived at the poles year round, didn’t migrate-even if it was a warmer time, this is just a colder area than the equator-shows that maybe dinos could handle the cold-this could speak towards endothermy
Biogeographic Evidence -isotopes
-basically can figure out temps by looking at isotopes-if look at isotopes across one tooth of dino, can estimate what temp living in-what graph shows is what map shows-looks like some dinos migrated, during summer go to mountains, then down to plains when colder-so they did some migration-modern mammals do this-so maybe what they did to avoid being too cold was just keep moving to the warmest places
TO SUM IT UP, ecology argues for endo or ecto?
- endo
- Dinosaurs have the same predator prey ratios as mammals-1 carnivore for every 10 herbivores in modern endothermic ecosystems-in ectothermic ecosystems, a little diff, don’t need as many herbivores to support a carnivore cuz their energy levels aren’t as high
TO SUM IT UP, cardiopulmonary evidence argues for endo or ecto?
- endo
- Dinosaurs have 4-chambered heart and lung air sacs like birds, and may have had one-way airflow-this evidence is a little bit equivocal cuz of crocodiles being a little peculiar, but still points to endothermy
TO SUM IT UP, Insulation evidence argues for endo or ecto?
- endo
- Dinosaurs had insulating feathers, like fur or bird feathers
TO SUM IT UP, Bone and Growth rates argue for endo or ecto?
- endo OR ecto
- Dinosaurs have bone characters like mammals/bird with complex growth, but also show LAGs-this is more equivocal-so endo or ecto-but tends more towards endo
TO SUM IT UP, Neurophysiological evidence argues for endo or ecto?
- ecto
- Most dinosaurs have small brains for their body size, although some are as large as birds/mammals -could probably argue endo or ecto
TO SUM IT UP, Isotopic evidence (diff between core and extremity temp) argues for endo or ecto?
- endo
- Dinosaurs have inferred temperatures like birds/mammals and little difference between core and extremities (also like birds/ mammals)
TO SUM IT UP, skull features argue for endo or ecto?
- endo or ecto
- Dinosaurs may have had turbinates like birds/mammals do-but unclear
TO SUM IT UP, posture argues for endo or ecto?
- endo
- Dinosaurs have non-sprawling posture like birds/mammals
TO SUM IT UP, Biogeographic Distribution evidence argues for endo or ecto?
- endo
- Dinosaurs lived in cold environments (poles and mountains) although may have migrated-but some didn’t
So which is it????!??! (are dinos endotherms or ectotherms?)
- a lot of this evidence is equivocal-evidence for both
- can we give a definitive answer?
- maybe we’re asking the wrong question-maybe dinos did something totally different
- that’s what’s why we’re getting such weird answers when we try to answer the question this way-basically that’s what the Goldilocks Hypothesis is all about
The “Goldilocks Hypothesis”
- Animals can put energy into two diff things: maintenance (renewing cells, generating heat, finding food) or production (growth, reproduction, fat storage)
- can put some of energy into maintenance (day to day life things) or could put energy into production (the extra stuff-getting bigger, having offspring, etc)
- ectotherms and endotherms apportion energy differently
- ectotherms: 60% on maintanance, 40% on production
- endotherms: 97% on maintenance, 3% on production
- remember, being an endotherm is costly-most of energy goes into maintenance cuz have to maintain energy levels, maintain internal heat-costly-so endothermy not necessarily the best strategy as we often believe
- ectotherms tend to be pretty even in spreading energy between maintenance and production-can spend more energy on growth than endotherms, that’s why they have indeterminate growth, unlike endotherms
- what the Goldilocks hypothesis is, is that it says dinos were somewhere in between-not endothermic or ectothermic-but mesothermic
Dinosaurs as mesotherms
- dinos somewhere in between endotherms and ectotherms-They had intermediate metabolic rates, but burned energy like ectotherms (i.e., put relatively more energy into production)
- So, they could more energy into growth
- Remember, dinosaurs got bigger over time (Cope’s Rule) and probably were gigantothermic (meaning that although they didn’t generate their heat internally, they had a relatively constant body temp, just because they were big)
- what’s driving this growth in size is the evolutionary arms race (Red Queen Hypothesis-prey get bigger so predators get bigger so prey gets bigger and so on)
- ectotherms put more energy into production but tend to have a smaller pool of energy to draw from-just cuz they’re eating less, getting less energy in general
- endotherms have a large energy pool but put little of it into production-most of it gets put into maintenance
- dinos were somewhere in middle-this is why its the Goldilocks hypothesis-large pool of energy, and put lots of it into production-burn energy like an ectotherm, but have an energy pool like an endotherm-basically what this means is that dinos were doing something totally different (from modern species)-we just don’t have many good models for it today -the way it’s sometimes described as they can raise their body temp but they don’t defend it
Different Strokes for Different folks-Ectotherms
can put more energy into production, but have a smaller pool of energy to draw from
Different Strokes for Different folks-Mesotherms
have a large pool of energy, and can put lots of it into production (<–just right)
Different Strokes for Different folks-endotherms
have a larger energy pool, but can put little of it into production, because their maintenance is so costly
Mesotherms
- Raise their body temperature, but don’t ‘defend it’ -put energy into maintenance and increasing body temp, and then they become gigantothermic, and then they don’t defend it, meaning they don’t use energy to maintain a high body temp
- one of the lines of evidence for this comes from growth rates-rate in the middle between endo and ectotherms (for mesotherms and dinos)
- dinos fall in middle ground here between ectotherms and endotherms
Mesotherms besides dinos
- turns out there;s a few animals that fall in between that have this mesothermic body heat thing (examples below)
- Modern examples: tuna, echidna, sea turtles
- tend to have this metabolic middle ground-between endotherms and ectotherms-and some modern species have this too but not many-maybe dinos were the only ones filling up this space for a while, back in the mesozoic
But there’s a breaking point…
-If you increase metabolic rate TOO much ….
- you become fully endothermic
- This may have happened to some lineages of theropods
- One line of evidence of this– they’re the main group to develop feathers -all dinos have some kind of featherlike structure but theropods do it to the extreme
- Also, some theropods become herbivorous – more energy at lower tropic levels, in plants
- And there are no giants in these lineages -so there’s lineages that lead to birds don’t get very big
- And some become birds…
- May also explain why there are no small dinosaurs (in other lineages) or marine dinosaurs (because they couldn’t do that without going over the line and becoming endothermic)
So the answer to our question (of dino endo vs ectothermy) is that dinos….
- were probably a mix of ecotherms and endotherms and many of them probably fell in between
- May have changed their metabolic as they grew-huge dinos start out really small-maybe were endothermic as younger, became ectothermic and gigantothermic as got older
- Some taxa were probably more to one end or the other…
- so “are dinos ecto or endothermic?” is not a good question
- there is no good answer
- the answer is that they’re somewhere in between-they’re in between
Charles Darwin
(not sure if need to know for final)
- Born in England, mother died when he was 8, father physician, out on house calls, raised by older sisters
- lived off his father’s money until he made him get a job
- went to Edinburgh University to become a doctor-fell in love with natural history-met some botanists and geologists-decided didn’t want to be a doctor
- trained to be a parson at Cambridge-a country priest-less formal than what we think of as priests now-priest that local people would go to, hold small services
- this was a good job for someone of his (high) class-something that kids had nothing to do, what they did-but while he was training, he got asked to go on a voyage on the Beagle as a naturalist (to keep captain company mostly, since captain was high class and didn’t want to socialize w low class sailors-and do some natural history stuff)-2nd choice, 1st couldn’t go-Beagle was a ship of the navy, travelled the world, map coastline of south america-important strategically cuz England had holdings there
- Darwin did a lot on the ship though-get off boat, hire guide, take a mule or horse and meet boat farther down coast cuz got seasick-made a lot of observations during this
- while on this trip got kinda famous-sending reports back to newspapers in England-when came back was pretty famous cuz he had a column, people reading it
- publishes book when he gets back, basically lives the rest of his life as an author
- marries cousin Emma-not uncommon at the time
Darwin Timeline
-1839-publishes first book, on the Beagle voyage
-also marries his first cousin, Emma Edgewood
-1840-develops his mysterious illness-people have debated what this illness was-due to stress about thinking of publishing his theory of evolution? tropical disease picked up on his trip? psychosomatic? he spent the rest of his life mostly at home sick
-1843 moves to Dorn house with Emma-lived the rest of their lives there-had 11 children, 2 died in infancy
-1851-daughter Annie (favorite, helped him with science stuff) dies-huge event in Darwin’s life-changed his outlook on life, probably views on religion
-1858-presents an abstract on the Origin of Species
-1859-publishes the full book-later goes through 6 editions
-does lots of work and publishing from home after this
1882-died-friends and supporters (esp Thomas Huxley) petitioned to have him buried in Westminster Abbey-buried with honor there
Darwin’s publications
- published 19 books
- talked about animals he found on his trip on the Beagle
- published 6 version of Origin of Species
- did not mention man in this book-but later published a book called the Descent of Man-more of his ideas on human evolution
- published books on biology, barnacles, animals, scientific inquiry, etc.
Theropods
- a diverse group of bipedal saurischian dinosaurs
- birds are actually the descendants of small nonflying theropods
- The most popular group of dinosaurs
- Both with the public and paleontologists – 40% of all dinosaur species named
- Most debated group in dinosaur studies
- Extremely diverse taxonomically and ecologically – But rare in the fossil record (10-20% of finds) -so amount found disproportionate to how many in ecosystem
- Widely distributed – present at every dinosaur fossil locality
theropods-herbivores or carnivores?
- Carnivores!!!
- Most are carnivorous with recurved, pointed teeth, some with serrations
- Characterized by intramandibular joint
theropod skulls-compact or no?
- Pneumatized Skull
- Lots of air spaces to lighten the skull
- Both between and within bones
- Seen in the post-cranial skeleton as well
- very small brain-most of the space in skull filled w air
- air sacs
- Similar to human sinuses-we have air sacs as well, called our sinuses
theropod brains
- Trend toward larger brains (in relation to body) -in some
- Some later taxa have EQs similar to birds
theropod senses
- Enhanced hearing and smell
- Stereoscopic Vision
theropod senses-Stereoscopic Vision
-when look T rex head on-eyes pointing towards you-means field of view of the 2 eyes cross over each other-gives depth perception (=the diff in position between your 2 eyes that tells you position)-many predators have this cuz helps catch prey-prey usually has eyes more on sides, so get wide range of vision to detect prey
theropods- bipedal or 4 legs?
Bipedal
- small and bipedal-many dinos evolved to walk on 4 legs later-but these guys stuck w 2 legs
- Only group to retain full obligate bipedality
- Much longer hindlimbs than forelimbs *
- Digitigrade *
- Reduction in digits I & V *
- 5 sacral vertebrae *
- Stiffened tails *
- =Running (Cursoriality)
theropods-Forelimb Characters
- Loss/reduction of digits IV & V as all dinos do(and sometimes III)
- Some opposability of digit I -can kind of grasp
- some dinos had really short arms-but short limbs were still strong! may have been used for something diff-to hold down prey? mating? unclear-but although small, weren’t weak
Theropod size
Huge Diversity in Size
- Tyrannosaurus rex (6000kg) to Mircoraptor (1kg)
- If you include modern birds the difference from smallest (hummingbird) to largest is 5,000,000x !
- largest terrestrial carnivore today is the polar bear, which is 10x smaller than T Rex
- T. rex largest terrestrial carnivore to have ever lived! in terms of mass
- Other theropods may have been taller than T. rex, but none heavier (probably)
- but not all theropods were big
were theropods the only predators around?
- other things around that weren’t theropods that were eating meat-more of them than theropods-and even out of theropods, most of them were small theropods
- dryadissector=another small predator that was common
Herrarasaurids
- South American
- Mid-Late Triassic (230Ma)
- Possibly basal theropods
- Possibly basal dinosaurs
- Defined by lack of characters
Coelophysids
- Mainly small, North American & African forms
- Late Triassic and Jurassic
- Coelophysis-most numerous dinosaur fossil
- Ghost Ranch Site, NM - all traveling in herd, killed in flood, lots of fossils in one area-La Brea tar pits?
were Coelophysids cannibals?
bones in animals found of some small organisms-originally thought these were bones of small Coelophysids -so were cannibals, older eating the young-some species do this, territorial thing, take over pack and eat young so know any future young are its own-maybe the case here-but now found that probably weren’t cannibals, were eating some other small animals
Abelisaurs
-Primarily Gondwanan – S.Amer, Africa, Madagascar, India, maybe Europe – Biogeographic implications -Mostly Cretaceous -Some have “headgear”
Ceratosaurs
- Horned dinosaurs
- Mainly Gondwanan
- Mainly Cretaceous
Tetanurae
- name means “Stiff Tail”
- Further reduced digits
- Loss of IV & V (as all dinos) and III reduced/lost (diff from other dinos)
- More pneumatized heads-extra skull hole-in front of antorbital fenestra
- Pubic foot
- Muscle attachment for muscles that move the tail
Spinosaurs
- Mainly Cretaceous
- Large, but lightly built
- Some have sail-backs – Why?
- Some piscivorous (long thin snouts with lots of little teeth-to catch fish)& semiaquatic (spent some time in the water
- Includes Megalosaurus
- long thin snouts with lots of little teeth
- Recent finds of a more complete skeleton
- Some now think they were semi-aquatic -thicker ribs-use to help them sink in the water-these guys had some ribs that looked similar to that-seen in modern animals like manatees-this is debated
What were the spines in Spinosaurs
used for?
- Thermoregulation?-maybe these guys were still ectothermic
- Cooling?
- Heat storage? like backpack to store heat and fat
- Cooling?
- Display? maybe colorful to attract mates
- Support? tendon that runs all along spine and to head-helps hold head up-patterns along spine like that make easier to hold head up, with the help of the tendon
Ratio of spine head to vertebral body size in dinos
-Dinosaurs more similar to mammals with humps for fat or support than to sail-backed mammal-like reptiles
Allosaurs
- Middle Jurassic to late Cretaceous
- Laurasian
- Some atain large sizes, but most are medium sized
Cleveland-Lloyd Dinosaur Quarry
-Central UT
-Species Counts:
– 44 Allosaurus
– 6 other theropods
– 9 sauropods
– 5 ornithopods
– 4 Stegosaurus
-Predator Trap! Locality was in sticky mud near a river bank-know cuz 10x more carnivorous than herbivores (looking at species found above)-should be other way around because of 10% energy transfer up pyramid-we talked about this before-prey got stuck, predators thought easy catch, went in and got caught too, kept happening
Coelosaurs
-Many convergent on earlier Allosaurs and Ceratosaurs
-Characterized by:
– Arctometararsals- metatarsals wrap around each other and are interlocked
– Semilunate carpal - relates to their ancestry to birds-relates to how birds come out of this group
Compsognathus
- Late Jurassic of Europe
- Near-shore islands
- “Turkey-sized”
- Probably feathered
Tyrannosaurs
- Late Cretaceous of Asia and North America, possibly also Australia
- Further digit loss – Arm use?
- Robust skulls-thick-restist hard forces, protect
- Dilong – feathered Tyrannosaur
- lots of variation in size-much more diversity in this group that people think! Cuz people usually just think of T rex
Ornithomimosaurs
- Cretaceous of Laurasia – Possibly also Gondwana
- many become omnivorous & herbivorous -so not all theropods are carnivorous!
- Some have bizarre osteological adaptations – E.g., Duck-like beaks
Alvarezsaurids
- Cretaceous of S. & N. America and Asia
- Short, stout forelimbs, with reduced digits-wrist bones fused together, then one huge finger
- would use stout fingers to dig up social insects-ants and termites-poke at them and pull out parts-maybe these guys were the anteaters of the Cretaceous
- didn’t have much in terms of teeth
Maniraptors
-Characters:
– Breast bones present in some
– In some the pubis faces backward like birds (and ornithischians)
-Possibly primitively omnivorous
-small
-may have evolved flight independently from birds-and in diff way-some had wings on front limb and hindlimb-gliders?
-some debate on their relationship to birds-do birds come from this group, or are they a separate group altogether?
microraptor gui
smallest dinosaur!
Oviraptors
- Late Cretaceous of Asia and N. America
- Misidentification of eggs gave them their name-originally thought were stealing eggs, but later realized were sitting on own eggs
- Similar to Ornithomimosaurs
- reinforced toothless jaws make have been used for crushing hard objects, e.g., clams
Therizinosaurs
-hyper-specialized giant forelimbs
-huge gut-digested plants in there, didn’t grind up in mouth
-Possibly analogous to giant ground sloths
-Cretaceous Laurasian in distribution
– Falcarius – from N. Amer. Oldest member of the group
Deinonychosauria
- “Terrible claw”
- Late Jurassic to Cretaceous
- Some possibly arboreal
- Some possibly omnivorous
- Group that birds are derived from
Overview -Triassic dinos:
Coelophysids and Herrarasaurids
Overview: Jurassic Dinos
– Laurasia
Allosaurs, Compsognathus, Deinonychosaurs
Gondwana
-Abelisaurs, Ceratosaurs
Overview: crestaceous dinos
Laurasia:
-Spinosaurs, Allosaurs, Tyrannosaurs, Ornithomimosaurs, Alvarezsaurids, Oviraptors, Therizinosaurs, Deinonychosaurs
Gondwana:
-Abelisaurs, Ceratorsaurs, Spinosaurs, Ornithomimosaurs (?) Alvarezsaurids (S.A.), Tyrannosaurs (?)
-increase in diversity in taxa and ecological groups, land changing, dividing
Evolution of large theropods (within ceratosaurs, allosaurs, tyrannosaurids) shows:
1) Increase in head size
2) Increase in tooth size.
3) Increase in jaw muscle mass (deeper jaw, larger adductor chamber.)
4) Greater skull rigidity.
5) Reduction in distal elongation.
Allosaurus vs tyrannosaurid killing techniques
Whereas Allosaurus may have killed by repeatedly applying relatively weak slashing bites and backing off (killed over time), large tyrannosaurids used more forceful crushing bites-nipping strategy (to get strips of flesh in tight spots) and “puncture and pull” biting
- like cats (tigers) and (wild) dogs today
- Dogs tend to attack in packs with many small nipping bites that wear down (large) prey (okay that it’s large cuz hunt in packs)
- Cats tend to be solitary, and kill with powerful “killing bites” and use their limbs
T Rex bite model
-nipping strategy )to get strips of flesh in tight spots) and “puncture and pull” biting
2-5 metric ton T.rex probably killed ____ and _____
ceratopsians and ankylosaurs (3.5-8 tons)
T rex ____ prey, didn’t _____
crush, didn’t nip
The Large Carnivore Macroevolutionary Ratchet
- Pervasive selection for large body size leads to the evolution of hypercarnivory (a diet of large prey)
- And this in turn leads to increased vulnerability to extinction.
- so as get bigger, eat larger prey-can’t live off little prey anymore cuz can’t get enough of them fast enough-and as get bigger, tend to get smaller population sizes, so more prone to extinction
- IF you are carnivorous, and selection favors larger size, THEN ….. energetic constraints will favor adaptations for taking large prey, and ….
- These specializations for hypercarnivory and large body size will result in reduced population densities, and vulnerability to extinction.
- Evolution of large size and dental specialization leads to a decline in evolutionary versatility (the ability to adapt to new conditions).
- EVOLUTION IS NOT PRESCIENT!
Advantages of size increase?
1) Predator avoidance-top of food chain, stronger, less predators after you and can defend self well
2) Can kill wider range of prey species.
3) Improved thermal efficiency.
4) Advantageous in interference competition-if you kill something, you get to eat all of it-don’t have to take a piece and run-no one will fight you for it/kick you out-Intraguild predation and carcass theft are significant among big predators. Body size often determines the winner.
theropods certainly ate ____
other theropods
If body size increase is accompanied by enhanced adaptations for hypercarnivory, then:
a) population density will decline, and
b) species will become more vulnerable to extinction.
-evolution of size leads to decrease in ability to adapt
evolution doesn’t care about extinction-just cares about fitness of individual-if bigger, easier to survive-evolution leads to improvement on individual level but extinction on species level
How fast could theropods run?
-Estimates done with modeling:
– Allosaurus & Tyrannosaurus 4-11m/s (9-25mph)
– (Much) faster speeds for smaller taxa
-look at modern animalis, mass to speed ratios-then try to do same thing for dinos, use other models to help
-t rex was probably not a fast runner-9-25 mph-so fast, but not cheetah fast-fast enough to run down a human at the higher end
-smaller dinos probably moved a lot faster
Was T. rex a predator or scavenger? Evidence for scavenger:
- Relatively small eyes
- Enhanced smell(smell rotting animals, draws them in)
- Relatively slow speed
- Tiny forelimbs
- Piercing teeth-for taking off big parts of flesh and crushing bones like modern hyenas
Was T. rex a predator or scavenger? Counterevidence to the scavenger evidence:
- Large absolute size of eyes even if relatively small for their head
- Smell can be used to find living as well as dead
- Prey were slow too-so didn’t matter than t rex was slow
- Some modern predators don’t have useful arms either – wolves, secretary birds, etc.
- Teeth similar to crocodiles
- Obligate scavengers (if only eat already dead pray-there’s an energetic cost-have to move around quickly, get to it before competitors, takes a lot of energy-so) need to be soaring vertebrates (i.e., vultures) due to energetic costs
- found an animal that was attacked by a T Rex and healed and survived-evidence that T Rex went after living animals
Was T. rex a predator or scavenger? answer:
-probably somewhere in the middle-T Rex was the biggest thing around-it’ll eat whatever it wants-probably wasn’t an obligate scavenger but an occassional scavenger
Tyrannosaur Growth
- Behavior probably changed during growth
- Younger individuals were smaller and faster
- Older individuals were slower and probably ate bigger prey
- High mortality among neonates-probably had a lot of offspring, prococious, went out to get prey, but these smaller young were probably prey themselves-so a lot died, but those who survived went to top of the food chain
Tyrannosaur Diversification
- May have tracked changes in sea level
- Changes in sea level may have led to isolation and migrations-led to speciation
- this is what gets done with modern animals esp birds-looking at why so many species, relate to environmental things
A holistic approach to theropods
-model skulls to look at biting, teeth to look at diet-lots of things going into this, holistic thing-looking at all diff aspects of Tyrannasaurus biology to figure out characteristics
Dinosaur Decomposition
- oviraptor nest with decayed skeletons found
- found evidence on bones of animal of flesh-eating beetles-same ones we see today
- use now to ready skeletons to get put in museum collections-get rid of all flesh
- used for forensic work too-can tell how long it’s been out based on how many life cycles of these beetles have happened
Major Plant Groups in the Mesozoic
- important cuz drove evolution of sauropods
- Pteridophytes
- Gymnosperms
- Angiosperms
Major Plant Groups in the Mesozoic: Pteridophytes
- vascular tissue & spores
- Horsetails
- Ferns
Major Plant Groups in the Mesozoic: Gymnosperms
- naked seed plants (have seeds, but not encased in fruit)
- Cycads
- Ginkgos
- Conifers
Major Plant Groups in the Mesozoic: Angiosperms
- have seeds, but encased in fruit-flowers turn into fruit
- flowering plants
Horsetails (Sphenophytes)
- Develop ‘fruiting body’ that releases spores
- Need water to germinate because they have spores
- Modern taxa (“Equisetum”) are small
- Mesozoic taxa reached 30P (10m) tall
- adults don’t really have leaves-young only have thin ones
- long, thin, flexible plants
- much more diverse group in the pst-much bigger part of ecosystem
Ferns
-Two stage life-cycle
– Sporophyte – gives off spores
– Gametophyte – a developing spore
-so basically like if egg and sperm left our bodies then lived on own for a while before coming together
-Need water to germinate
-Tree ferns grew to immense sizes (although not as large today)
Cycads
-Aka “sego palms”
-Dioecious -male and female plants are separate
– Male plants give off pollen
– Female plants have seeds
-Thick leaves to resist predawn
-Much more diverse in Mesozoic
Ginkgo
- One living species -“Ginkgo biloba”
- Dioecious-usually just see the males though?
- First ‘woody’ plants
- Stinky seeds that “reptiles” like
Conifers
-Modern cedars, cypresses, firs, junipers, pines, redwoods
-Mesozoic podocarps and “monkey puzzle trees”
– “Lollipop” morphology
– Restricted to southern continents today
-some are monoecious (having male and female reproductive structures), some dioecious
-now restricted to southern continents, but much more widely spread throughout mesozoic
Angiosperms
- Flowering plants
- First ones in the early Cretaceous-start to take over by end-but early on, limited -take over because they can grow very quickly-almost like weeds-come in and take over area that’s been recently cleared-so dominant group when you think of plants
- Often with male and female reproductive parts in the same flower
- Seeds covered by a fruit
- Many are faster growing than gymnosperms
- rise of Angiosperms coincides with rise in insect pollinators and herbivores
plant diversity over time (increased or decreased?) ____
increased for angiosperms-the rest stay about the same-except early vascular plants die out
Reconstructing a paleo-forest
- Permian (300Ma) forest from China with exquisite preservation
- Dominated by tree ferns with taller conifers and sphenophytes
- forests looked a lot diff than today
Climatic Variation across the face of the Earth Today-Location of the World’s Major Deserts:
all around these latitude lines (30 degrees north and south)-has to do with air circulation patterns-find diff plant communities today using this same reasoning
Climatic variation across the face of the Earth in the Jurassic
- Most of the plant (and dinosaur) diversity is in the midlatitudes (much like today. Equatorial regions more desert-like: hotter and dryer
- Due to hothouse conditions and continental position
- so we know kinda what the environment looked like back then, how it affected the plants and animals as climate changed
- by studying what happened in the past, may be able to get some knowledge of what happens in the future
Sauropods
-The largest vertebrates to walk the Earth!
-Originate in South America in the Triassic
-First radiation of dinosaurian herbivores
– Adapted to eat the tough plants of the midMesozoic (e.g., cycads & conifers)
-First extinction of a major dinosaur lineage – the prosauropods
-many early forms were still theropod-like
-400kg heart!! (about 900 pounds)
Titanosaurs were ____
the biggest animals that ever lived on land-but they weren’t born big
Triassic diversity
- a lot of diversity
- many early forms (of sauropods) were still theropod-like
sauropod head size
don’t need big heads cuz don’t do much chewing or processing in mouth-just using mouths to rip off plant material, swallow whole-then stomach does all the processing-fermentation, gastroliths
Sauropod Skull Modifications
-Large nares (nostrils)
– Move further posteriorly during their evolution
-Teeth built for scraping plants (not chewing)
-Two types of teeth
– Pencil (diplodocids)
– Thick leaf-like (brachiosaurs)
– Both probably for puncturing, not grinding
-Plant digestion by fermentation and gastroliths
Snorkeling Sauropods?
-An adaptation for living in the water?
– Probably not – too much pressure on the lungs
-maybe they had a trunk?
-many taxa that were found had nostrils pushed back, trunk-like structure-so maybe sauropods did have a trunk-not positive
-but the problem with this idea is that sauropods wouldn’t have sunk
Sauropod necks
-Elongated necks
-From both elongation of cervical vertebrae and increase in number
-Also elongate tails
-Thermoregulatory?
-Herbivory adaptation? so could get at higher trees
Neck Posture:
-straight up or held parallel to ground?
-probably not so upright-side to side, swing head, eat everything in a certain radius-so could get a lot of food
-some groups could lift head high
-Blood pressure estimates
-Computer modeling of neck motions
-Probably more side-to-side than up-down in most taxa
Apatosaurus
- genus of sauropod dinosaur that lived in North America during the Late Jurassic period
- range in age from about 154 to 150 million years ago
- cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and the bones of the leg were much stockier despite being longer, implying that Apatosaurus was a more robust animal
- The tail was held above the ground during normal locomotion
- Like all sauropods, Apatosaurus had only one claw on the forelimbs and three on its hindlimbs.
- skull similar to Diplodocus skull
- long/big
Diplodocus
- genus of diplodocid sauropod dinosaur
- double-beamed chevron bones located in the underside of the tail
- lived in what is now western North America at the end of the Jurassic Period
- classic dinosaur shape, long neck and tail, and four sturdy legs.
- For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators Allosaurus and Ceratosaurus
Sauropod Neck Adaptations
-Pneumatized vertebrae-lots of air, open space
– Lighten neck (and support?)
– Air Sacs?
-Neck (nuchal) Ligaments-area for spine to attach?
sauropod vertebrae
- different vertebral joints allow for differing range of motion
- can compare these dino spines and necks to other animals-to understand how worked
- like suspension bridge? long tendon down neck and back that helped keep head up
- hydraulic necks-head heads up with air sacs-filled up air spaces with air, like balloon, helped keep head up
- but not all had long necks-brachytrachelopan didn’t
Sauropods-Adaptations for Quadrapedality
-Short hind limbs – Longer forelimbs in some taxa -Shorter distal elements – Humerus > radius/ulna – Femur > tibia/fibula -Graviportal posture
Sauropod feet
- Graviportal Digitigrade feet
- Still on toes, with a foot pad posteriorly
- similar to modern elephant feet
- Clawed Feet
- Enlarged digit 1 on forelimb with claw
- Claws on digits 1-3 in hindlimb (in later forms)
- forelimb more digitigrade, hindlimb more plantigrade, in both diplodocus and apatosaurus
were Sauropods tripedal?
- use tail as another leg?
- probably did not do this-or if did, not often-probably only for sexy time to help keep balance, use claw to hold onto females
Trackways reveal ____
- sociality and stance
- upright posture as you’d expect from dinos
- travelled in groups or herds-shows some sociality
Sauropodomorphs
- Worldwide distribution
- 2 major groups: Prosauropods and Sauropods
Sauropodomorphs: Prosauropods
- Late Triassic – Early Jurassic
- First extinction of a major dinosaur lineage
- Long, narrow skulls
- Serrated, leaf-like teeth
- Facultative bipeds – Front limbs shorter than hindlimbs -can walk on 1 or 4 legs
- 10 cervical vertebrae
- Not as large as later sauropods (2-10m)
- necks not very long
Plateosaurus
- one of the best known dinos-many skeletons found, many complete
- a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago
- prosauropod
- As of 2011, two species are recognized: the type species P. engelhardti, and the slightly earlier P. gracilis
- a bipedal herbivore with a small skull on a long, mobile neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding
- large variation in size
- usually lived 12-20 years
- mass death site suggests sociality
Sauropodomorph: Sauropods
-Mainly Jurassic – except Titanosaurs that last through Cretaceous, mostly in Gondwana -Enlarged coracoid (on pectoral girdle) -Claws on hind digits 1-3 ->12 cervical vertebrae (necks bigger) -Further elongate tails -More elaborate vertebrae -two major lineages
diplodocids(diplodocus) vs macronarians (camarasaurs, brachiosaurs, titanosaurs)-diplodocids:
- single nostril opening-nares posterior and between orbits
- procumbent, slender peg-like teeth at anterior margin of mouth
diplodocids(diplodocus) vs macronarians (camarasaurs, brachiosaurs, titanosaurs)-macronarians:
- single nostril opening-nares posterior and between orbits
- procumbent, slender peg-like teeth at anterior margin of mouth
Barosaurus
- a giant, long-tailed, long-necked, plant-eating dinosaur closely related to the more familiar Diplodocus.
- Upper Jurassic period
“Brontosaurus”
- Apatosaurus ajax was named first (by Marsh)
- Brontosaurus excelsus was named later (also by Marsh)
- Were found to be part of the same genus, and Apatosaurus has priority
- when you discover 2 species are actually the same thing, go with older name, forget the newer one
camarasaurids, brachiosaurids, titanosaurids
can lift heads higher, cuz have forelimbs on ground, not bipedal
some titanosaurids develop ____
- dermal armor
- why? species recognition thing? don’t really know-interesting
Dinosaur National Monument
-NE Utah
-Jurassic
-Specimens of:
– Apatosaurus
– Barosaurus
– Camarasaurus
– Diplodocus
Sauropod Diets
-Probably ate lower quality plant material – tough parts of conifers and cycads
-Large size may have helped with digesting poor quality plant material
-May have prevented overgrazing
-Plants adapted to sauropods
– Another Red Queen race that drove them to bigger sizes-led to gigantism in sauropods
marked ____ in the number of herbivores and angiosperms in the late Crestaceous
increase
what dominated the Late Jurassic
huge herbivores and conifers dominated the forests. Herbivores created open spaces that favor weedy opportunists (angiosperms)
what dominated the early cretaceous:
low browsing herbivores and first angiosperms
what dominated the late cretaceous:
diverse low browsing herbivores and diverse angiosperms
Ornithischia Novelties
- ‘Bird’ hips (reverse pubis) – possibly to make room for big stomachs
- Leaf-shaped teeth
- Lower jaw with predentary bone
- Network of bony ligaments (called ossified tendons in lab)
– stiffen backbone
Ornithischians made up of:
ornithopods, marginocephalians, thyreophorans
Horns and Spikes-which dinos have them?
Thyreophorans & Marginocephalians
Thyreophorans
“Armored Dinosaurs”
- Characterized by osteoderms – “skin bones” or scutes
- Probably another “Arms Race” with theropods -like when species increase in size-this is another solution, to develop armor
- Herbivorous – with some specific adaptations for eating plants (only theropods can be carnivorous-but not all theropods are carnivorous)
- Also characterized by post-orbital processes
Osteoderms
-Form in the connective tissue layers of the skin
-Multiple purposes in thyreoporans
– Defense, display (sexual selection or species recognition), thermoregulation (may have helped them regulate body temp)
-Also found on titanosaurs (sauropods), other diapsids, and edentate mammals
Thyreoporan herbivory adaptations
- Small, leaf-like teeth, inset from the edge of the jaw (probably for cheeks)
- but probably didn’t chew a whole lot with this tiny little teeth-mostly just tore stuff up and swallowed
- Beaks (rhamphotheca) for nipping plants
- Possibly long tongues that could extend to pull of plant material – we think they had this because they had well developed hyoids -bone between voice box and tongue-usually mean attachment for some sort of muscular tongue
- Wide thoracic regions-kind of barrel shaped – fermentation vats (for fermentation of plant material)
Thyreoporan bipedality? or quadrupedality?
-most of these guys were quadrupedal (walked on 4 legs)
-Large forelimb to hindlimb ratio (1:2)-hindlimbs relatively tall compared to forelimbs
– Thickened limbs
-Wide stance and slow gait
– Possibly semi-sprawling forelimbs
-Low browsers-probably kept heads relatively low-couldn’t lift highs very high
-but hold tail up a bit, head not completely down
solitary or social
- Mostly Solitary
- No ‘mass graves’
- Pinacosaurus burial site in Mongolia is the only site with multiple individuals, including juveniles
- so they probably weren’t very common or very social
early forms of Thyreoporans
- Early Jurassic of Laurasia
- Possibly bipedal (facultative-could choose to walk on 4 legs or 2 legs?- or obligate)
- but eventually this group of dinos had to become quadrupedal so later forms quadrupedal
- scutellosaurus (SW USA), scelidosaurus (england)
scutellosaurus
- an extinct genus of thyreophoran ornithischian dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period
- is classified in Thyreophora, the armoured dinosaurs
- bipedal
- one of the earliest representatives of the armored dinosaurs and the basalmost form discovered to date
- a small, lighly-built, ground-dwelling, herbivore, that could grow up to an estimated 1.175 m (3.9 ft) long
scelidosaurus
-a genus of herbivorous armoured ornithischian dinosaur from the early Jurassic
-known for their excellent preservation. Scelidosaurus has been called the earliest complete dinosaur
-Only one species, Scelidosaurus harrisonii, is considered valid today
0about 4 metres (13 ft) long
-largely quadrupedal animal, feeding on low scrubby plants, the parts of which were bitten off by the small, elongated, head to be processed in the large gut.
-Scelidosaurus was lightly armoured, protected by long horizontal rows of keeled oval scutes, that stretched along the neck, back and tail.
-a basal member of the Thyreophora
-One of the oldest known and most “primitive” of the thyreophorans
Ankylosaurs
-mid Jurassic – end Cretaceous
-5-9m long
-Laurasia and Australia
– Maybe S. America & Antarctica
– Polar specimens known
-Conservative body plan– only change in size
-Two groups
– Ankylosaurids and Nodosaurids
– Differ in skull shape and placement of osteodern-but still basically have same body plan
Ankylosaur Skulls
- Broad skulls with armor covering sutures and the supratemporal fenestrae
- like had bones in scalp that eventually fused with skull-covered temporal fenestra, diff holes-all these little bones osteoderms fused to the skull
Ankylosaur brains
small
Ankylosaur teeth
-Teeth have cingula – ridges around the base
ankylosaurs nostrils-what do they indicate?
- tooting ankylosaurs?
- large blood vessels
- vocalization? - communication
- physiology? temperature regulation
- sensory? smelling
- weird complicated nostrils-maybe for some sort of mating call?-looks like trumpet where can make noise, modify noises
- some people think it was for temperature regulation-work like turbinates in nasal passages
- or maybe it was a sensory thing-neuron receptors in there for smelling things
- most like vocalization
